+#include "commit.h"
+#include "refs.h"
+#include "quote.h"
+
+#define DO_REVS 1
+#define DO_NOREV 2
+#define DO_FLAGS 4
+#define DO_NONFLAGS 8
+static int filter = ~0;
+
+static char *def = NULL;
+
+#define NORMAL 0
+#define REVERSED 1
+static int show_type = NORMAL;
+static int symbolic = 0;
+static int output_sq = 0;
+
+static int revs_count = 0;
+
+/*
+ * Some arguments are relevant "revision" arguments,
+ * others are about output format or other details.
+ * This sorts it all out.
+ */
+static int is_rev_argument(const char *arg)
+{
+ static const char *rev_args[] = {
+ "--all",
+ "--bisect",
+ "--dense",
+ "--header",
+ "--max-age=",
+ "--max-count=",
+ "--merge-order",
+ "--min-age=",
+ "--no-merges",
+ "--objects",
+ "--parents",
+ "--pretty",
+ "--show-breaks",
+ "--sparse",
+ "--topo-order",
+ "--unpacked",
+ NULL
+ };
+ const char **p = rev_args;
+
+ for (;;) {
+ const char *str = *p++;
+ int len;
+ if (!str)
+ return 0;
+ len = strlen(str);
+ if (!strcmp(arg, str) ||
+ (str[len-1] == '=' && !strncmp(arg, str, len)))
+ return 1;
+ }
+}
+
+/* Output argument as a string, either SQ or normal */
+static void show(const char *arg)
+{
+ if (output_sq) {
+ int sq = '\'', ch;
+
+ putchar(sq);
+ while ((ch = *arg++)) {
+ if (ch == sq)
+ fputs("'\\'", stdout);
+ putchar(ch);
+ }
+ putchar(sq);
+ putchar(' ');
+ }
+ else
+ puts(arg);
+}
+
+/* Output a revision, only if filter allows it */
+static void show_rev(int type, const unsigned char *sha1, const char *name)
+{
+ if (!(filter & DO_REVS))
+ return;
+ def = NULL;
+ revs_count++;
+
+ if (type != show_type)
+ putchar('^');
+ if (symbolic && name)
+ show(name);
+ else
+ show(sha1_to_hex(sha1));
+}
+
+/* Output a flag, only if filter allows it. */
+static void show_flag(char *arg)
+{
+ if (!(filter & DO_FLAGS))
+ return;
+ if (filter & (is_rev_argument(arg) ? DO_REVS : DO_NOREV))
+ show(arg);
+}
+
+static void show_default(void)
+{
+ char *s = def;
+
+ if (s) {
+ unsigned char sha1[20];
+
+ def = NULL;
+ if (!get_sha1(s, sha1)) {
+ show_rev(NORMAL, sha1, s);
+ return;
+ }
+ }
+}
+
+static int show_reference(const char *refname, const unsigned char *sha1)
+{
+ show_rev(NORMAL, sha1, refname);
+ return 0;
+}
+
+static void show_datestring(const char *flag, const char *datestr)
+{
+ static char buffer[100];
+
+ /* date handling requires both flags and revs */
+ if ((filter & (DO_FLAGS | DO_REVS)) != (DO_FLAGS | DO_REVS))
+ return;
+ snprintf(buffer, sizeof(buffer), "%s%lu", flag, approxidate(datestr));
+ show(buffer);
+}
+
+static void show_file(const char *arg)
+{
+ show_default();
+ if ((filter & (DO_NONFLAGS|DO_NOREV)) == (DO_NONFLAGS|DO_NOREV))
+ show(arg);
+}